The value of capillary electrophoresis as a separation and analytical technique has been recognized for some time. In capillary electrophoresis, a small tube or capillary is filled with an electrically conductive fluid, or buffer. A small quantity of a sample to be analyzed is introduced into one end of the capillary bore, the ends of the capillary are placed into separate reservoirs of buffer, and a direct current high voltage is applied to the ends of the capillary by means of electrodes positioned in the buffer reservoirs, causing a small current to flow through the capillary.
With the correct polarity applied across the capillary, the sample begins to migrate toward the other end of the capillary. As this migration occurs, different molecules in the sample travel at different rates, causing the sample to become separated into bands of these different molecules. These bands or groups of different molecules are detected near the other end of the capillary by, for example, passing a perpendicular light beam through the bore of the capillary. Changes to the light beam, such as absorbance caused by the different molecules, are detected as the separated molecules pass through the beam, thus identifying the different molecules or the classes or categories of molecules in the sample and the relative concentration of such molecules.
Capillary electrophoresis analyzers typically use a single capillary to perform an analysis. For example, European Patent Application number 89302489.3, publication number 0,339,779 A2, corresponding to U.S. patent application Ser. No. 07/188,773, filed Apr. 29, 1988 (Burolla) now abandoned, describes an automated capillary electrophoresis apparatus using a single capillary, as does U.S. Pat. No. 5,045,172 to Guzman. To increase throughput, however, a plurality of capillaries may be utilized in parallel, thus performing a corresponding plurality of capillary electrophoresis analyze simultaneously. An analysis employing parallel capillaries is disclosed, for example, in U.S. patent application Ser. No. 07,916,308 filed Jul. 17, 1992 issued as U.S. Pat. No. 5,413,686 on May 9, 1995, and entitled "Multi-Channel Capillary Electrophoresis Systems."
In such an analyzer, there is a need for easy replacement of the capillaries. Such replacement should be possible without the use of special tools. Further, the capillaries should occupy a relatively small volume within such an analyzer, and thus the capillaries should be as closely spaced as possible while retaining each capillary in a fashion that allows replacement by hand. Due to the closely spaced nature of such capillaries, there is also a need for capillaries that can be easily replaced in such a confined space with relatively little manipulation, which is particularly important given the extremely small diameter of such capillaries.
Thus, there is a need for capillaries and a capillary retaining system that is easy to use, can be operated by hand without the need for special tools, that readily lends itself to closely-spaced capillaries, and that requires a relatively limited amount of manipulation to remove and replace capillaries.